1. Field of the Invention
The present invention generally relates to a terminal connection device, and more particularly to a terminal connection mechanism for a power supply circuit supplying electric power to various electric and/or electronic devices.
2. Description of the Prior Art
In a task of mounting a terminal connection member such as a metal lead wire for a power supply circuit to a wiring board or substrate used with electric and/or electronic devices, processes of inserting and soldering the connecting member to the wiring board have been largely automated in recent years. The following briefly describes examples of a conventional terminal connection mechanism for a power supply circuit with reference to FIGS. 8 to 10.
As shown in FIG. 8, in the disclosure of Japanese Utility Model Laid-open publication (Jikkai) H1-60366 (in 1989), a battery terminal connection device includes a metal lead 4 which has a straight bridge portion 4C with a coiled spring terminal portion 4A at its one end and an insertion attachment portion 4B at its other end. The metal lead 4 is further provided with a tendril pier portion 4D at its bent portion between the bridge portion 4C and the insertion attachment portion 4B, where the tendril pier portion 4D has a spin loop configuration which is fixed and connected by solder onto a printed pattern layer 2 disposed on a substrate 1. The lead attachment portion 4B is inserted to, but not fastened in, a through hole 6 formed in the substrate in order to prevent the bridge portion 4C from falling over, thereby facilitating the soldering.
In this construction, however, since the connecting lead member is fixed by solder to the substrate by one part thereof, therefore the terminal configuration is ineffective as a means of keeping the connecting member from falling over, that is, the terminal configuration is minimally self-supporting.
A further drawback to the above-noted configuration is that any force applied to the bridge portion is also directly applied to the solder joint of the tendril pier portion 4D, resulting in causing solder cracks and possibly continuity problems.
Yet another drawback is that soldering the tendril pier portion onto the wiring board necessarily increases the overall thickness. As a result, this configuration is unsuited to thin electronic devices.
In another conventional example as shown in FIG. 9, the Japanese Utility Model Laid-open publication (Jikkai) H2-110180 (in 1990) teaches a terminal connection device which includes an elastic metal lead 4 disposed on an insulating substrate 1, where the metal lead 4 has an incurvated loop portion 5 of generally U-character shape protruded downward. The U-shaped loop portion 5 is inserted and securely held in a slot 3 formed at only one location in the substrate 1. In this configuration, by defining the length L of the slot 3 slightly smaller than the outer diameter D of the loop portion 5, the loop portion 5 is elastically engaged in the slot 3. The loop portion 5 held in the slot 3 is fixed and connected to the peripheral printed pattern layer 2 by soldering 7.
However, since this terminal configuration is fixed by solder at only one location, there is a problem in that minimal self-support is provided. In addition, vibration of the substrate, metal lead wire, or lead terminal can cause the wire loop to come out of the hole.
A further problem with this configuration is that the minimum curvature radius R of the typical U-shaped loop portion 5 is necessarily at least three times the diameter d of the lead wire when the loop portion 5 is formed using a coiling machine. This makes it difficult to reduce the overall thickness of the device because of a large height H of the projected loop portion. That is, the height H of the loop portion protruded from the dielectric substrate is thus at least three times the diameter d of the lead wire (i.e., H.gtoreq.R.gtoreq.3d). Therefore, the thickness of the finished dielectric substrate assembly increases, and this conventional terminal configuration is thus unsuited to thin electronic devices.
In further another example as shown in FIG. 10, the Japanese Patent Registration Publication No. 2658586 (i.e., Laid-open Publication H4-242082) discloses a terminal connection device which includes an elastic metal lead 4 disposed on an insulating substrate 1, where the metal lead 4 has an incurvated loop portion 5 of generally U-character shape and a straight bridge portion 4C with a coiled spring terminal portion 4A at its one end and an insertion attachment portion 4B extending downward at its other end. The U-character shaped loop portion 5 is protruded downward and inserted into a slot 3 formed in the substrate 1 to be thereby elastically engaged therewith by defining the length L of the slot 3 slightly smaller than the outer diameter D of the loop portion 5. The loop portion 5 engaged in the slot 3 is fixed and connected by solder 7A to a peripheral printed pattern layer on a back surface of the substrate. The insertion attachment portion 4B is inserted into a through hole 6 formed in the substrate and then fixed and connected by solder 7B to a peripheral printed pattern layer on the back surface of the substrate. Thus, the lead loop portion can be securely held in the slot 3 in the substrate with effective self-supporting performance, avoiding occurrence of solder cracks.
In this conventional construction, however, the height H of the loop projection portion protruded downward from the dielectric substrate is likewise required to be larger than three times the diameter d of the lead wire (i.e., H.gtoreq.R.gtoreq.3d). Therefore, the thickness of the finished dielectric substrate assembly increases, and these conventional terminal configurations are thus unsuited to thin electronic devices.